The use of electronic devices such as computers, mobile phones, and audio/video equipment has had enormous development in the world in the last decades. A lot of effort has been made in making smaller electronic devices, in particular for portable use, such as mobile phones, laptop computers, Personal Digital Assistants (PDA), mp3 players, and so on. Much help has been obtained from the miniaturization of electronic components and the development of more efficient batteries. In mobile communications, the communication systems have gone from analogue to digital, and at the same time the dimensions of the communication mobile phones have gone from briefcase size to the pocket size phones of today, in only a couple of decades. Still today, mobile phones are getting smaller and smaller and the size is generally considered to be an important factor for the end customer.
Regarding mobile phones as well as portable computers and PDA:s, the end users have a number of conflicting requirements. Basically, the device should be as small and light-weight as possible. Furthermore, it should provide more and more advanced functions, have a long battery time, and have a user-friendly interface. Still, there is only so much space in an electronic device, and in order to be competitive the elements of the device must be carefully packaged. The compact size of e.g. mobile phones also means that the user interface, typically a display and a set of keys, is limited. In order to access the different functions and stored items, different types of menu systems are often employed. Still, it may sometimes be difficult to find certain items if it is less than obvious under which menu label to search.
In the field of digital photography, the concept of tagging has gain a lot of interest in the past. A tag is like a keyword or category label, which can be assigned to a digital photo, and is helpful for finding photos which have something in common. Typically, it is possible to assign as many tags as you wish to each photo. Furthermore, if photos, i.e. image files, are stored where they are accessible by more than one person, such as on a network server, it may also be possible for different users to add different tags to the photos.
If, on the other hand, a user wants to recall if a certain phone call has been placed of answered, it is generally possible to search a call register for a trace of the call, unless it has been deleted. Similarly, if a user is anxious to check if and when a message was sent or received, the message inbox and outbox, respectively, may be investigated.
A problem related to the issue of tracing past events carried out by means of an electronic device is that different types of events have to be investigated in different ways, and through different menu channels. This makes searching for event records time-consuming and increases the risk of missing what you are looking for.